This signal interrupts
by Rowan Arkenson
Summary: AU: Sirius gets sorted into Slytherin. Set mostly in fifth year. "Sirius was good at copying Severus' answers when he wasn't looking, and at staring out of dungeon windows into dungeon corridors, and at flying when no one else was around." Warning for slashy times.
1. A Prologue: Part 1

_A Prologue_

Sirius stood stock still, hearing the awkward silence chime and echo inside the bubble that had formed around his family. On the platform there were hundreds of kids – a few slightly shorter, but most taller, some the sort of taller that Sirius thought only grownups did – who were laughing and crying with their families. It wasn't all good news, he could tell, but at least there was some level of _noise. _That was what had struck him most, leaving his house for the first time that summer in over two months: a summer of quiet tiptoeing round corners and through narrow hallways, waiting to be called upon, waiting to be talked to, waiting to be instructed, months of quiet waiting. The level of noise that London could produce had surprised him, despite having experienced it before, but _this –_ this collective and growing noise of wizards and witches being excited and sad and happy all at once – this was something Sirius had never heard before.

He looked up at his mother, trying to mask his face. He waited for her to speak, unsure of her mood. She smiled at him. "Have a safe journey," she said, sounding polite, as if she were seeing off a distant relative who had outstayed their welcome.

"Thank you," Sirius replied. He turned round to speak to his brother, but Reg had vanished. "Where did Reg go?" he asked his mother.

"He's gone back to the car," replied his mother, smile wavering. "You know how your father doesn't like to wait around. Now, off you go, the train is leaving in ten minutes." Sirius was aware that ten minutes was more than enough time to say goodbye properly, but he wasn't any more interested in saying it than his mother was. "Ok," was all he said, and he pulled his suitcase towards a train door.

He heaved it up onto his knee, grasping the handle and, half pulling half pushing, managed to squash it on along with all the other luggage. He grabbed a small bag which contained a sandwich and got on board.

The train was busier than he expected it to be, somehow. Maybe it was the size of it. The Hogwarts Express was big, bigger than he expected from the photos he had of it, but it was still impossibly small compared to the vast number of children that were running up and down its corridors. Everyone seemed to have friends already, and something inside Sirius tightened. He thought of Reg, and was surprised to discover how much he missed his younger brother in that moment. Sirius made a quick decision and opened the third compartment door to his right.

Inside were three boys, one owl and a cat. One of the boys looked up curiously but the other two were in quiet, polite discussion, so Sirius sat down, uncertain of how he should sit or where he should look.

"Hi," said one boy quite brightly, and Sirius looked at him in relief. He wasn't one of the tall ones, but looked about his age, and from the fact that he had introduced himself Sirius guessed that this was a carriage of first years too. He braved a smile. "Hello."

"I'm James," said the boy, who had black hair, unfashionable glasses and a wonky, if persistent, smile. "Who are you?"

Sirius hesitated. It occurred to him, looking at the other two boys in the carriage who were sat opposite each other and seemed to be exchanging conversation about whether they had any siblings already at Hogwarts, that everyone in this room was on the same level. They were all new, didn't know each other, perhaps didn't know anyone. No one knew about Sirius' family, or even Sirius, at all.

"My name's Sirius," he answered, trying to mirror the wonky grin that James had given him. In his moment of confidence Sirius even looked next to them. "What at your names?"

"This is Remus and Peter," replied James, indicating with a wave of the hand that Sirius missed in all his furious concentration at being somebody different which boy was who.

"Hi," said the smallest boy who was sat next to James, stroking the ginger cat on his lap with enthusiasm. The cat, on the other hand, looked vaguely bored and was staring out of the carriage window, perhaps wondering when its next rat might appear. "This is my cat Kerriwinkle," he added, wrinkling his face slightly as he said it. "Family name," he muttered, as if that was supposed to explain something that Sirius hadn't understood.

"Right," replied Sirius, then, "cool. I don't have a pet."

"Not even an owl?" James asked in disbelief. Sirius shook his head, glancing at the boy sat next to him who was fiddling with the straps on his cloak. "Oh you have to get an owl, surely your parents will get you one," he said, speaking fast, as though this were the most obvious thing in the world, and that perhaps Sirius' parents had just forgotten. "Mine is a screech owl, so I've called her Screech." He beamed with pride, and Sirius wasn't sure if he was supposed to laugh or wince. He merely nodded.

At that moment the door opened and a red-headed girl walked in. Sirius glanced at her and then back to James as she sat down beside Remus, next to the window. "Maybe I'll ask for one for my birthday," Sirius said, knowing it was an empty thought.

"You could get a screech owl, then they could be friends," suggested James. From the fact that he had already known the names of the other two boys in the carriage and had been smiling constantly, as if to put Sirius at ease, he could tell that he liked him already.

"Do you play chess much?" asked James. Sirius shook his head, but the small boy looked up from his cat eagerly.

"I do!" The two then entered a spot of banter which Sirius droned in and out of, not having played chess before himself. He realised he would have to learn. James was laughing with Peter as the door opened for what Sirius thought must be the last time, as there was only one seat left in the small compartment, and a boy with scraggly black hair walked in and sat opposite the girl. They started chatting and Sirius looked at his knees. "So," he started, turning to the boy to his side, "do you play chess too?" The boy with brown hair didn't smile, but opened his mouth to speak, before James interrupted loudly.

"_Slytherin_?" he'd almost shouted with disdain, a look of incredulity on his face. Sirius' stomach dropped, and he raced back through the last five minutes in his head, wishing he had chosen a different compartment, wishing he hadn't decided to be someone else, wishing he'd just stayed quiet. "Who wants to be in Slytherin," went on James, talking directly to the new boy. "I think I'd leave, wouldn't you?" Sirius realised with some horror that this last part had been directed at him, as James looked to him for some back up.

He swallowed, and slouched in his seat slightly. "My whole family have been in Slytherin." The words came out of his mouth before he'd had time to double check them.

"Blimey," said James, "and I thought you seemed all right!"

A short moment passed, during which Sirius weighed up his options. He could sit, quietly, side with the new boy in the carriage, who hadn't said a word to him, side with his brother, and parents, and decades and decades of Blacks before them, all of whom had (if he believed his mother) gone to Slytherin and then gone on to be all right sort of people. But he thought of his mum, and the bored smile she had given him before he left.

Making a quick decision, Sirius grinned at James. "Maybe I'll break the tradition."


	2. A Prologue: Part 2

_A Prologue Continued_

The sun outside had warmed to an orange glow, and the train begun slowing down. Sirius was adjusting the wide sleeves of his new black cloak against his arm, feeling the weight like a cloud sinking against his chest. The boy and the girl who had sat by the window had left an hour ago, after an argument about houses had erupted. Sirius knew the name of the boy – Severus – as James had wheedled it out of him in an attempt to make some point about bloodlines. Sirius had stayed mostly quiet, as had Remus and Peter. The girl had eventually lost her temper, calling James an arrogant toad and pulling Severus out of the carriage with her. Severus had looked pleased, and it had made Sirius wonder how long they had known each other, if they were friends, or brother and sister maybe. It made him feel quite alone. Even seeing the easy way that James spoke to the three of them made him feel alone, although Remus was quite as quiet as he was. Peter and James had laughed and been silly together and Sirius had had a conversation with Remus about where they were both from and if Remus had any brothers or sisters at Hogwarts. He didn't, only a younger sister, the same age as Reg. It was quite a short conversation.

But now the train was pulling into the station and Sirius was concentrating hard on not feeling nervous, so that it wouldn't show in his face. "Let's go," said James, grinning, walking away as part of his robes fell over his shoulder. Sirius adjusted his and followed.

The platform was chaos. There was a line of children Sirius' height shuffling towards one corner, settling underneath the tallest oak Sirius had ever seen. It sheltered the station in its shadow against the orange sky as the older kids left, walking confidently off the platform and into the unknown distance.

"Mum and dad told me we have to travel to Hogwarts in boats across a river," James told Sirius as they walked forwards together. A very, very large man was rustling up students and shouting at them to follow him, and James and Sirius fell into suit, Remus and Peter chatting softly behind them.

"Really?" Sirius said, surprised. "That seems like a pretty muggle way to travel." 

"My mum told me it's to make sure none of us are half demon," said James, "because demons can't cross running water." He chuckled, so Sirius laughed too.

"Wouldn't that count out all of the Slytherins?" he said, feeling hollow in his chest as he thought of his family and James laughed appreciatively.

At that moment Severus and his friend walked past, and Sirius fell silent, hoping James would do the same. He did. A second later when Sirius looked up, he thought he knew why.

The river – lake, actually – across which they were to row (boats glittered along the bank that had sprung up in front of them as they left the shade of the trees) was like nothing Sirius had ever seen before. He had always lived in London: had seen beauty in the greenest parks and the tallest buildings and in impossibly busy streets and impossibly loud nights. But this.

"That's beautiful," breathed a voice behind them, and Sirius turned to see Remus with his small face turned slightly upwards, taking in the lake, and the nightsky, and the shining halfmoon, and the castle.

The castle was just... "It's pretty big," James offered. He looked stunned for the first time that day, but it didn't last very long. The corners of his mouth twitched upwards. "This is going to be _awesome_," and for some reason Sirius didn't think he was referring to the valuable seven-year learning experience ahead of them. They had all seen magic, all been accidentally practising it for eleven years, but none of them had ever spent so much time with people their own age, in a place that looked impossibly busy and loud and wonderful. Sirius couldn't help it. He smiled, and looked at Remus, who looked at him straight in the eye for the first time that day, and grinned.

.

"The sorting ceremony," the tall witch was shouting as they were all hurrying into the massive hallway, Sirius intending to listen but being amazed by size of the place he was standing in, "will decide whose house you are in. There are four houses named after the founders of Hogwarts: Gryffindor, Hufflepuff, Slytherin and Ravenclaw. Your house will determine where you sleep, who you take your classes with, and who you score house points for. The house system is a tradition as ancient as Hogwarts itself, and it is the hope that you will treat said system with respect, treating your fellow housemates like family, and gaining points for good behaviour which may earn you the house cup at the end of the year." The witch took a few moments to stare round at them all earnestly, before continuing.

"Who's that?" Sirius whispered to James. He had missed her name in all the excitement.

"Professor McGonagall," James whispered back. "Transfiguration professor." Sirius had no idea how James knew so much about Hogwarts. They both came from magical families, both their parents had gone to Hogwarts, and yet Sirius felt he might as well have been muggle-born for all his mum had prepared him.

Suddenly the doors were open, and the small crowd of first years were surging forward. The Great Hall itself was enormous, and Sirius had difficulty taking everything in. They were walking up the middle, moving through long tables and benches of students. Some were watching them as they walked in, others chatted away, too busy catching up after the long summer break to be bothered by the new kids. Sirius swallowed.

There hadn't been enough time. Somehow, he thought he'd have more time. He thought there'd have been more time, between arriving and being sorted. He didn't know what he wanted.

"How do you know what house you want to be in?" he asked James in desperation, speaking in a low voice.

James looked at him, startled. "Well, it doesn't really matter," he replied, looking distractedly up at the teachers' table. "The hat sorts you, you don't get to choose." 

"Oh," Sirius said, feeling disappointment and relief rush into him all at once. "Brilliant." James frowned at him but Professor McGonagall had started talking again and a hush fell over the room.

The students were called up one at a time, and as the first girl walked shakedly towards the stage, Sirius looked round at the crowd, wondering if James and Peter would really be sorted into Gryffindor like they wanted, given that they didn't have a choice over the matter. He spotted Remus standing behind Peter, and wondered which house he wanted to be in. Or which house would suit his personality. He didn't know much about the others, only Slytherin. He only knew that people in Slytherin house were more clever and successful than those from other houses. He glanced at Severus and the girl who looked as though they had not finished arguing, and wondered which was the happiest one.

"Black, Sirius," McGonagall was saying, and Sirius jumped slightly. He felt his heart hammer in his chest as he walked slowly forward. McGonagall handed him the oversized sorting hat with a blank expression and Sirius turned round, finding an entire room of people staring at him. His cheeks began to blush, and he closed his eyes as he sat on the small stool. The hat fell down, softly, over his eyes. Sirius felt a million things rushing at him all at once, and his breath quickened.

_What's the problem?_ came a voice inside his head. Sirius knew, without knowing how he knew, that the hat was talking to him. He shifted, uncomfortable.

_I'd like to be friends with James, and the others_, he thought, _but I don't want to upset my family. _He felt surprised at the strength and shape of the feeling.

There was silence from the hat, while he thought, _I don't want to disappoint them._

_And?_

_A__nd I don't want to be the only one._

_And?_

Sirius opened his eyes then, and his gaze flicked to James, who was staring back.

_I just want my parents to like me._

He looked away from James as the hat shifted above his head, the call of 'Slytherin' ringing loud and clear across the room.


	3. Chapter one - Moons

**A/N: It's been a while since I started this, but I've had a renewed burst of inspiration. Chapters may be short, but hope you enjoy!**

**-Rowan**

Chapter one – Moons

Meeting the fifth year Gryffindors in corridors between classes had grown to feel tiringly clichéd. Sirius Black could feel the tiredness etching into his bones as Severus stiffened beside him. "Hey, do you smell that?" the other boy muttered to him out of the corner of his mouth.

Sirius grinned, though he couldn't remember deciding to do so. He raised his face and voice as James came into full view. "Oh I see what you mean Sev," he replied, frowning and wafting a hand under his nose, "smells like blood traitors." A few paces behind them, Sirius could hear Avery laughing.

James Potter laughed too. "That's hilarious Black," he said, stopping a few metres away from Sirius. Lupin and Pettigrew had been looking for something in Lupin's bag but stopped at the sound of Black's name. "Considering the fact that we _like _it when you prejudiced gits call us blood traitors."

"Doesn't make you any less disgusting," Severus said, smiling in an almost polite way.

"Like you can talk, _Snivellus_," James said, smile gone and turning towards Sev. Peter chuckled behind Potter, and it made Sirius want to throw his wand away and punch Pettigrew in the face. Potter at least held his own with the Slytherins – the thing Sirius liked, and disliked, the most about him – but Pettigrew was always a step behind, hiding and giggling. Pathetic.

Sirius stepped towards Pettigrew aggressively. Peter gasped and stepped backwards, tripping over his school robes and falling over. Sirius, Sev and Avery laughed and walked past the Gryffindors as Potter and Lupin helped Pettigrew to his feet.

They headed down towards the dungeons and went into their common room. The other fifth year boy, Stamford Mulciber, was sitting with two sixth years, Wilkes and Rosier. They were all on the Slytherin quidditch team together. Wilkes was the captain, a chaser, Rosier a beater and Mulciber the seeker. Sirius wasn't sure he liked any of them very much, but that didn't seem to both anyone. Sirius, Severus and Avery joined them at the table in the coldest corner of the emerald and silver triangular room.

"What's with you?" asked Severus.

Sirius snapped his head up. "Sorry?"

Severus gave him a quizzical look and then started to get his homework out.

It wasn't really Severus to ask questions. Sirius looked back at the wall, considering. After a few minutes he said, "It just annoys me that we still don't know where they go. If we could find out and tell Dumbledore, I'm sure they'd get expelled."

Severus was scratching on his parchment with his quill as he spoke. "Where would the fun be in that?" he mused, ducking as a red beam of light shot over his head. A portrait on the wall just above the head of a second year boy caught on fire, and Mulciber and the others were laughing. "Look," said Severus, looking up as he finished writing a sentence, "we're finding out Saturday night, right? You're not going to chicken out are you?"

"Of course not," Sirius snapped. "I just don't know if I can manage another three days staring at Potter's stupid face."

"So stop staring then." Severus had his head back in his bag, searching for another book, so Sirius couldn't tell whether Severus was smirking or if he was just imagining it.

Once a month, Potter, Lupin and Pettigrew disappeared for a night. It wasn't like Sirius was in the habit of following his enemies' every move, so this had taken years for him and Severus to notice. They had happened to be sneaking to the Gryffindor tower to fill the common room with stinkbombs when they were knocked to the floor. It felt like something had been passing by them, although neither had seen anything at first. But when Sirius quickly lifted himself off the ground and looked at the end of the corridor he saw Potter briefly, struggling with a cloak, before vanishing again.

This had been towards the end of Sirius' fifth. It had taken another month before Sirius saw them again, Potter and Pettigrew running out of the main entrance, whooping and cheering, Sirius on his way back from a walk. Another month before he realised that these sightings had happened four weeks apart, and a few more over the Summer holidays and into the beginning of fifth year of persuading Severus that they should find out if the Gryffindors were up to something before Severus pointed out that the first two recorded instances had happened on the full moon.

The next full moon was the coming Saturday, the second weekend back at school after the Christmas break. Not that Sirius had gone home this year.

Watching Severus working while the others messed around and some older students tried to put out the magical fire made Sirius feel tired, but it also made him feel guilty. He ran his hand across his forehead then reached for his bag.


End file.
